The identification and classification of the yeast genus Saccharomyces is of practical importance because some species are used in industries such as the beer, wine, baking and in biotechnology industries. Moreover, certain medical disorders are caused by yeast infections and appropriate treatment depends upon proper identification and classification of the species.
For example, excessive colonization of the intestine with yeasts can create large amounts of alcohol (gastrointestinal alcohol fermentation). This condition, called "alcohol autointoxication syndrome" or "autobrewery syndrome," can lead to painful disturbances in the health of patients. The ability to readily identify the causative agent of such a condition would be valuable.
Also, it is known that following infection with S. cerevisiae, immunosuppressed patients can contract a fungemia, a sometimes fatal disorder. Rapid and unambiguous identification of the involved yeasts could contribute to speedy therapy.
Further, the ability to differentiate various types of yeasts could be used to identify yeasts more rapidly in investigations of the type undertaken by Preller et al. J. Air Waste Managm. Ass. 39: 1094-1097 (1989). There, chronic, non-specific pulmonary disorders frequently appeared in the inhabitants of a town located near a yeast production plant and a penicillin production plant. In order to evaluate which yeasts were linked causally with this disease symptom, investigators determined the number of S. cerevisiae particles per cubic meter of air in region between the yeast production plant and the town. A rapid test would have permitted speedy identification of S. cerevisiae, and would have distinguished S. cerevisiae from other yeast species, such as, for example, Rhodotorula, which is frequently present in the air.
According to J. P. van der Walt, Genus 16: 555-718 (1970), 41 species are assigned to the genus Saccharomyces. However, many of these species have been assigned to other genera and renaming has taken place within the Saccharomyces genus. Currently, ten species are accepted within the Saccharomyces genus. See Barnett, J. A. Yeast 8: 1-23 (1992). These ten Saccharomyces species are: S. bayanus, S. castellii, S. cerevisiae, S. dairensis, S. exiguus, S. kluyveri, S. paradoxus, S. pastorianus, S. servazzii, and S. unisporus.
Moreover, in the future this classification likely will change because the rules and criteria by which taxonomic categorization of yeast species is undertaken are being changed. For example, one could argue that the species S. bayanus, S. paradoxus and S. pastorianus are not independent species but rather are varieties of S. cerevisiae.
Pursuant to Naumov et al. Yeast 8: 599-612 (1992), the following terminology is used for describing the present invention: Saccharomyces cerevisiae, Saccharomyces bayanus, Saccharomyces paradoxus and Saccharomyces pastorianus are combined as "Saccharomyces sensu stricto," in contrast to "Saccharomyces sensu lato", which is used to designate Saccharomyces castellii, Saccharomyces dairensis, Saccharomyces exiguus, Saccharomyces kluyveri, Saccharomyces unisporus and Saccharomyces servazzii. The yeast species are classified taxonomically first and foremost by morphological and physiological criteria (such as, for example, the utilization of carbon sources, dependence on growth factors, utilization of nitrogen sources, and the like) and also by mating behavior. DNA analysis also is used increasingly for determining relationships between yeast genera and yeast species.
On the other hand, immunological methods are only rarely employed for differentiating yeast species. One reason for this is that antibodies which are directed against cell wall-specific antigens cross-react to a large extent, both within a genus and beyond genera. The reason for the cross-reactivity within the genus Saccharomyces is that the cell wall-associated glycoproteins carry carbohydrate side groups which are made up of mannose chains that do not differ, or differ slightly, from species to species. There is also such a high degree of structural homology at the level of the polysaccharides (mannans and glucans) that any differentiation using antibodies would seem to be very difficult to achieve.
The difficulty in obtaining antibodies which are specific for a particular yeast species, in particular S. cerevisiae, is evident, for example, from Kumar et al. Infection and Immunity 1840 (1985), 806-812). The authors report that antibodies which were in each case prepared in rabbits against a representative of the species Histoplasma capsulatum, Candida albicans or Saccharomyces cerevisiae in each case also cross-react with the antigens of the other two species.
Consequently, a need exists for antibodies which react specifically with one or a few yeast species and thereby render it possible to use these antibodies to differentiate these yeast species from others. Such antibodies would be useful in certain foodstuff industries, such as the beer and wine industries, in the medical diagnostic industry and in the pharmaceutical industry for quality control purposes.
For example, monoclonal antibodies specific for Saccharomyces sensu stricto would be valuable in monitoring the culturing of S. cerevisiae (syn. S. boulardii) for use in drugs for treating diarrhea or for preparing recombinant proteins of S. cerevisiae. Such monoclonal antibodies also would be useful for diagnosing conditions such as "alcohol autointoxication syndrome," fungemia, and non-specific pulmonary disorders.